Cancer is a widespread and deadly disease. Although a variety of therapeutic strategies are currently used for treatment of cancer, for many cancers these treatments do not offer a permanent cure for the disease. Significant improvements in the treatment of cancer have proven difficult to develop. Currently, the standard to measure the success of a new anti-cancer drug is often an increase in the survival of cancer patients in terms of months, not in years. There is a need for improved agents for the treatment of cancer.